Check out Fcntl.
from the man page(unfortunately the perldoc page doesn't go into enough detail):

F_SETFL  Set  the descriptor's flags to the value specified by arg.  
                Only O_APPEND, O_NONBLOCK and O_ASYNC
                may be set; the other flags are unaffected.
[download]

There is also some suggestions here (you can find with search)

FAQ - How do I open a file without blocking?

non-blocking accept

I will also recommend:

On asking for help

How to ReadTheFineManual

know thy FAQ - search is your friend

grep

grep> chown linux:users /world